How to transfer terror funds

A plot for a thriller I may write some day:

The counterterrorists are trying to track the transfer of terror funds to some nasty group. But the terrorists are wily. They establish a relationship with a corrupt or sympathetic businessman in the target country, with a courier adding a substantial sum to the businessman's account. They then communicate with the confederate via onetime pads and the internet. Once a month, the confederate takes out a onetime cipher pad and uses it to decipher a message on a neutral content internet site or in a piece of "spam," whereby the second letter of every word is part of a secret message.

Upon decoding the message, he destroys that pad sheet, of course.

The message may instruct "do nothing," or it might tell him to withdraw x amount and deliver it to an agent.

Well, I can't reveal how the terrorists are tracked. Don't want to reveal intelligence sources and methods, you know. Or spoil the plot.